Apparatus for performing sonication

ABSTRACT

An apparatus for performing sonication on liquid samples comprises a rack for holding an array of sample vials, an ultrasonic probe with an arrangement of recesses corresponding to the array of sample vials and adapted to respectively receive and contact an outer surface of a bottom portion of a respective one of the sample vials, and a counter-holder with an arrangement of pushing members corresponding to the array of sample vials and adapted to respectively apply a force to a respective one of the sample vials so as to push the bottom portion of each vial into contact with the associated recess of the probe. The apparatus can be used in a method of preparing a sample for detection of cell components (e.g. cell analyte, proteins, nucleid acids etc.) and applying sonication within certain parameter ranges which can provide a universal lysis method that can be applied to a large variety of cells or organisms like all bacteria, viruses, spores, yeast and mold within the same apparatus and process.

The present invention relates to an apparatus for performing sonicationon liquid samples, preferably in the field of biology, molecularbiology, biotechnology, biochemistry, general chemistry, food andbeverage industry, pharmaceutical industry and for use in diagnosticapplications in general. The invention moreover relates to a method ofpreparing a sample for detection of cell components using the apparatusfor performing sonication.

Sonication is used in the above fields for a number of uses such asmixing, solubilization, driving chemical reactions, tissuehomogenization, cell operation and uses, shearing of biologicalmolecules such as DNA as well as cleaning, plastic welding, etc.Sonication in these fields (except for plastic welding) is normallyperformed in bath sonicators where water transfers the sonic energy froma transducer to a sample, or with probe sonicators where a metal probeimmersed into the sample applies the sonic energy to it. Bath sonicationis limited in the amount of energy it transfers to the sample. Probesonication could supply substantial energy but is limited to one sampleat a time or one sample per probe. Furthermore, immersing the metalprobe(s) into the sample necessarily contaminates the metal probe andrequires costly cleaning.

Samples to be processed by sonication may comprise bacteria, cells,viruses and other materials containing the nucleic acids to be assayedin a suitable solution which is added in a predetermined volume to thesample container.

Most of the current devices for performing sonication on liquid sampleare limited as to the minimum volume of sample liquid they can treat orprocess at one point of time, thereby providing only a limitedthroughput, or suffer from other disadvantages like excessive cleaningrequirements after use.

The document US 2009/0151459 A1 discloses a system and method forultrasonic sample preparation which includes a cylindrical samplecontainer formed from a polymeric material and having a wall defining anouter peripheral side surface and an inner volume of between about 1 mland about 25 ml for containing a sample material. An external converteris provided which converts AC electricity to mechanical vibrations inthe ultrasonic range, and an ultrasonic probe is provided to be incontact with the outer peripheral surface of the sample container. Theultrasonic probe is in communication with a converter and transmits themechanical vibrations to the wall of the sample container and thereby tothe inner volume to excite and mix the sample material in the container.The probe has a probe portion which is not inserted into the samplecontainer but makes intimate contact with the peripheral side wall ofthe sample container. This prior art is a manually operated system andis restricted to sonication of a single sample in a single samplecontainer at one time.

The document EP 0337690 A1 discloses another method and apparatus forpreparing sample nucleic acids comprising non-invasive sonication of thesample contained within a sample container brought into physical contactwith an elongated vibrating ultrasonic tip of a sonicator resonating ata frequency of 40 kHz or greater. The ultrasonic transducer is mountedon a frame member, which in turn is mounted upon a base located within ahousing. The ultrasonic transducer is mounted upon a pneumatic cylinderfor controlling the force of the ultrasonic tip against a disposablecuvette serving as a container for the sample liquid. The cuvette ismaintained against the ultrasonic tip by a force retainer which slidablyengages the top of the cuvette. To maintain the contact between theultrasonic tip and the cuvette, the apparatus applies a pressure of6×10⁴ to 2×10⁵ Nm⁻² through energizing the pneumatic cylinder. Thisapparatus is also a one-sample-at-a-time apparatus and is therefore notsuitable for high-throughput applications.

The document US 2007/0238090 A1 discloses another system and method forprocessing a biological liquid sample for use in lysing viruses orbiological cells for analysis using biological assay systems. The samplevolume to be treated by this system is in the range from about 1 ml to10 ml and the sample is processed by applying pressure and either sonicenergy or thermal energy to the sample. To this end the apparatus has aspecific vial that is cylindrical and has an internal chamber forreceiving the sample. The vial has an open upper end into which a plugor insert for sealing the open upper end is inserted and a retaining capfor holding the plug in the vial by a threaded engagement with the upperexternal end portion of the vial. A heater coil surrounds the lower endof the vial and a sonication head in the form of an elongated tip islocated so as to face and contact a flat lower bottom end face of thevial.

In one further embodiment the document US 2007/0238090 A1 discloses anapparatus where the above structure with a specific vial and theassociated elongated sonication head is multiplied so that the pluralityof different samples can be simultaneously processed. This system has amulti-well plate having a plurality of wells or chambers, each forreceiving a sample of predetermined size, a plug plate having aplurality of plugs or plungers projecting from one face for sealingengagement in a respective aligned well in the multi-well plate, and alocking or latching mechanism for securing the two plates together wheneach plug is fully inserted into the respective well. A heater isprovided for heating the sample in each well and an ultrasonic devicehaving a plurality of elongated tips equal to the number of wells in theplate is used to apply ultrasonic waves to the sample in each well inthat the multi-probe sonication device is aligned with the lower ends ofthe wells and moved towards the wells until each probe contacts the flatbottom end face of the respective aligned well.

This embodiment is improving the system in a sense that it allows thesimultaneous processing of a larger number of samples but it is a verycomplicated arrangement requiring especially the multitude of ultrasonicprobe tips.

It is the object of the present invention to provide an apparatus forperforming sonication on plural liquid samples which is suitable toperform the sonication on a number of samples simultaneously and whichis more simplified and more robust than prior devices. Furthermore, itis an object of the invention to provide a method of preparing a samplefor detection of cell components by means of sonication that caneffectively perform a lysis on a number of samples in a largeapplication field.

To solve this problem the present invention provides an apparatus forperforming sonication on a liquid sample as defined in claim 1 and amethod of preparing a sample for detection of cell components using suchan apparatus as defined in claim 11. Preferred embodiments of theapparatus and of the method are defined in the dependent claims.

The apparatus of the invention for performing sonication on liquidsamples comprises a rack for holding an array of sample vials, anultrasonic probe with an arrangement of recesses corresponding to thearray of sample vials and adapted to respectively receive and contact anouter surface of a bottom portion of a respective one of the samplevials, and a counter-holder with an arrangement of pushing memberscorresponding to the array of sample vials and adapted to respectivelyapply a force to a respective one of the sample vials so as to push thebottom portion of each vial into contact with the associated recess ofthe probe.

The method of preparing a sample for detection of cell componentsaccording to the invention comprises the steps of providing the samplein a sample vial, placing the sample vial in the apparatus of theinvention, performing sonication on the sample in the sample vial by theapparatus using the following parameters to effect a lysis of thesample: applying a mechanical stress in between the sample vial and theprobe of 0.1 to 1 N/mm², applying a peak-to-peak amplitude of vibrationof 2 to 10 μm, and applying a frequency of vibration of 20 to 100 kHz.

One advantage of the apparatus is that lysis by way of sonication can beperformed on plural samples in the array simultaneously, wherein thesamples are received in standard vials or containers that are commonlyused as consumables in the field of biochemistry, general chemistry,food and beverage industry, pharmaceutical industry and for use indiagnostic applications in general, to carry out micro-reactions in themicroliter-range. These vials typically comprise conical laboratorytubes, so called 50 ml conical centrifuge tubes or round-bottom-tubes,1.5 ml or 2 ml microcentrifuge tubes, that are individually held in therack, or microtiter plates that combine an array of wells or test tubesin an integral plate, and are typically made from plastics materialsincluding PP (polypropylene), PS (polystyrene), PC (polycarbonate), PET(polyethylene) or thin glass.

By allowing sonication of the samples in such standard vials orcontainers, even very small amounts of sample liquid can be lysedefficiently because the probe by way of its arrangement of recessescorresponding to the array of sample vials respectively receives andcontacts an outer surface of the bottom portion of each respective oneof the sample vials. The small amount of the sample liquid commonlycollects at the bottom portion of each such vial, which is typicallyconical or round or semi-spherical. The recess of the probe surroundsthat bottom portion not only at the lower end face but also at a part ofthe length above the bottom end and thus maximizes the surface area andencircles the entire liquid volume. Thus, more energy can be transferredto the sample without the danger of melting or breaking the vial tubeand without requiring cooling of the vials during sonication. Moreover,the energy is more homogenously distributed and applied to the completevolume of the sample.

The indirect sonication from the outside of the vial avoids contact ofthe ultrasonic probe with the sample liquid and the fact that an arrayof plural sample vials can be sonicated simultaneously within the rackby the common ultrasonic probe provides a fast result and a highthroughput for large quantities of samples to be processed whileinvolving only a limited variation between the samples in the array.

The apparatus moreover provides an easy-to-use system since the holderof the rack for the samples is designed to be moved into contact withthe ultrasonic probe, which may stand still in the apparatus, so thatthere is a defined movement by way of a simple mechanical mechanism thatincreases safety for the users operating the apparatus. The simplemechanical arrangement provides the possibility of automating thetransport of the rack holding the array of sample vials into theoperating position which could be inside a substantially closed housingsealed from the environment. Therefore, the apparatus does not requiremanual handling steps during the process and only an arrangement of thevials into the rack of the apparatus as a preparatory step.

In that the ultrasonic probe is an integral block that has an array orarrangement of recesses corresponding to the array of sample vials andformed to respectively receive and contact an outer surface of a bottomportion of a respective one of the sample vials, i.e. in that the shapeof the recesses mimics the shape of the bottom of the vials, the contactarea with the outer surface of the vial is maximized and transfer ofultrasonic energy is concentrated on that part of the vial where thesample liquid collects even in case only very small amounts of sampleliquid in the microliter-range are treated. Thereby, even very smallamounts of sample liquid in the range of 20 μm to 1 ml can be sonicatedusing standard vials or containers available as consumables in theindustry.

The structure of the ultrasonic probe also provides the advantage thatthe sonication energy is homogeneously distributed with respect to allthe sample vials in the array so that the deviation between energyamounts applied at the respective positions is small and thecomparability of the results throughout the entire array is secured.

A particularly advantageous embodiment is one where the plural recessesin the ultrasonic probe are each configured so as to match differentbottom configurations of at least two different vials. This considerablyincreases the universal application of the apparatus and the speed ofthe sonication because no modification of the apparatus is required if adifferent type of vials/containers is to be processed from one batch tothe next.

Since the ultrasonic probe is provided with the arrangement of recessesand otherwise forms an integral block for all the sample vials to beprocessed in the apparatus, the structure is simple and the excitationof each liquid sample is comparable within narrow ranges. Thisfacilitates processing of larger numbers of samples and makes resultsmore comparable. Furthermore, the simple structure of the ultrasonicprobe facilitates cleaning of the apparatus in cases where sample liquidspills out from the vials/containers.

The method of preparing a sample for detection of cell components of theinvention using the apparatus of the invention and applying sonicationwithin the parameter ranges of claim 11 provides a universal lysismethod that can be applied to a large variety of cells or organisms likeall bacteria, viruses, spores, yeast and mold within the same apparatusand process. This reduces the number of different procedures that haveto be implemented and documented in a laboratory and makes theprocedures more simple and comparable to each other.

These and other aspects will become apparent from the description of apreferred embodiment below in connection with the attached drawing. Inthis drawing:

FIG. 1 shows a perspective schematic view of an exemplary embodiment ofthe apparatus of the present invention,

FIG. 2 shows the kinematic diagram of the apparatus of FIG. 1,

FIG. 3 shows a probe in cross section with different exemplified typesof recesses representing different preferred embodiments and enlargedcross-sectional views of the individual recesses within the ultrasonicprobe of the apparatus of the invention.

The basic configuration of the apparatus of the invention is shown inFIGS. 1 and 2. The apparatus has a rack 1 for holding an array of samplevials 2 and an ultrasonic probe 3 with an arrangement of recesses 4corresponding to the array of sample vials and adapted to respectivelyreceive and contact an outer surface of a bottom portion 2 a of arespective one of the sample vials when the probe and rack are alignedand brought into a working position shown in FIG. 1. The probe 3 iscooperating with a converter that produces the ultrasonic vibration andtransmits it to the probe.

The rack 1 is supported so as to be movable in the direction of thecenter axes and is preferably elastically biased in a direction towardspushing members 6 of a pushing mechanism 7 of a counter-holder 5 forapplying a holding or contact force. A moving mechanism (not shown) ispreferably provided in the apparatus for moving the rack between aposition outside of a housing of the apparatus and a position inside thehousing aligned with the ultrasonic probe. Thus, an operator only has toplace the vials with the samples into the rack or place the entire rackwith the vials on the moving mechanism. These motions can be performedby hand but can also be automated, for example by dedicated orprogrammable manipulators or robots. After initiation of the process(i.e. by pushing a “start”-button) the rack is automatically moved intothe housing, preferably by a horizontal movement, and sonication isperformed while the operator is shielded from the process. After thepreset sonication time has lapsed, the rack is again moved out from thehousing by the moving mechanism for further handling of the vials.

The counter-holder 5 has an arrangement of pushing members correspondingto the array of sample vials and adapted to respectively apply a forceto a top of a respective one of the sample vials 2 so as to push thebottom portion of each vial into tight contact with the associatedrecess 4 of the probe 3 with a defined pressure (force per surfacearea). The pressure is sufficiently high that a maximum of ultrasonicenergy is transferred to the sample in the vial and not to the vialitself in order to avoid the melting of the vial material (i.e.polypropylene) at the interface. A loss of contact would in fact createa shearing at the interface which would increase the temperature. On theother hand, a too high contact pressure would demand too much power fromthe power converter in order to maintain a constant vibration amplitudeand could create stress at the border of the vial which could have thesame negative consequences as loss of contact.

The force for creating the contact pressure could be created in a numberof different ways in the apparatus. In the shown preferred embodimentthe pushing members are preferably in the form of pushrods 6 that arearranged and held in a common platform 8 to apply the force to the topportion of the respective associated vials and to be moved together bymeans of a drive mechanism 9. A different configuration of the pushingmembers and a different place where the force is introduced into thevials are feasible. In a preferred embodiment (not shown) the array ofpushing members is exchangeable to accommodate a different array ofsample vials and/or sample vials with different configuration.

The pushrods 6 are preferably designed such that the force is adjustableand/or the pushrods are elastically biased towards the vials. This canbe achieved by pre-tensioned springs of which the pre-tension isadjustable to tune the force applied to the respective vial.

The positioning mechanism 9 is provided to selectively move the platform8 and thereby engage the arrangement of pushing members 6 with thevials. This positioning mechanism 9 comprises the platform 8 for holdingthe array of pushing members 6. The platform 8 is supported so as to beat least movable in the direction towards and away from the probe 3 anda drive mechanism 9 for repeatedly alternatingly moving the platform 8between these positions and apply the same holding force may comprise acam/follower system with a gear and a drive motor as shown in FIG. 2.Other drive mechanisms including electric, hydraulic or pneumatic driveactuation are feasible. The pushrods 6 could also be biased by electricor hydraulic cylinders (not shown).

The arrangement in the apparatus is generally such that the center axesof the associated recesses and pushing members are aligned and areconcentric with the associated sample vials in the array, at least whenthe force is applied and the sonication is started.

The recesses 4 of the integral block-like ultrasonic probe 3 of theapparatus as shown, for example in FIG. 3 are an important aspect of theinvention. The recesses are formed to match, at least to a certainextent, a bottom configuration of the bottom portion 2 a of the vials 2to be used in the array, wherein the recesses are preferably rotationalsymmetrical about a center axis and, depending on the type of vial usedin the apparatus, preferably either hemispherical or conical as shown inFIG. 3 a. Thus, the apparatus can be used in connection with commonstandard reaction vessels or vials or containers which could be groupedinto small vials/containers having a typical rated volume or size in therange of 1.5 ml to 2 ml, i.e. so-called Eppendorf cups, that typicallyhave a snap cover or conical seal or silicone seal, or largevials/containers which are typically in the rated volume in the range of15 ml to 50 ml that have a snap or screw cover and that are, forexample, available as 50 ml conical centrifuge tubes or 96-well plateswith 200 μl wells.

The vials can be individual containers as described above or microtiterplates that combine an array of wells or test tubes in an integralplate. All these containers are typically made from plastics materialsincluding PP (polypropylene), PS (polystyrene), PC (polycarbonate), PET(polyethylene), or from thin glass. The small types of vials typicallyhave a small hemispherical tip end and the larger types of vials have aconical lower end but different configurations are possible. As shown inFIG. 3 a the recesses of the ultrasonic probe of the invention aremimicking these bottom configurations of the vials that are typicallyused in the laboratory environment. Thereby, the contact area with theouter surface in the bottom section is maximized and the contact area isnot only restricted to the axial bottom surface but extends furtherupward so that the contact area between the recess and the vialsurrounds the lower bottom end where the small volumes of sample liquidcollect.

In a particularly preferred embodiment that is shown in FIG. 3 b, eachrecess is configured so as to match different bottom configurations ofat least two or even more different vials. Such a structure as shown inFIG. 3 b combines the semi-spherical contour for the small types ofvials at the lower portion with the conical configuration of the largetype of vials adjacent to the bottom end in one recess. Here, too,different configurations can be implemented that provide maximum contactarea with the different configurations.

The apparatus of the invention can be applied universally to a largenumber of lysis tasks on liquid samples in the field of biology,molecular biology, biotechnology, biochemistry, general chemistry, foodand beverage industry, pharmaceutical industry and for use in diagnosticapplications in general. In that the common sample vials/containers asdescribed above can be accommodated in the apparatus and in that theparameters of the sonication process like holding force on the samplevials, peak-to-peak amplitude of vibration, and frequency as well assonication time can be set in the apparatus, a wide variety ofapplications like mixing, sono-chemistry, and sample preparation fordiagnostics can be carried out.

A particularly advantageous effect is obtained by using the abovedescribed apparatus in a method of preparing one or more sample(s) fordetection of cell components (e.g. cell analyte, proteins, nucleic acid(NA), etc.) which thus comprises the steps of providing each sample in aseparate sample vial, placing the sample vials in the apparatus,performing sonication on the samples in the sample vials simultaneouslyby the apparatus using the following parameters to effect a lysis of thesamples:

-   -   applying a holding mechanical stress in between the sample vials        and the probe of 0.1 to 1 N/mm² (preferably 0.26+/−0.05 N/mm²        for 1.5 ml microcentifuge tubes and 0.1+/−0.01 N/mm² for 50 ml        conical centrifuge tubes);    -   applying a peak-to-peak amplitude of vibration of 2 to 10 μm        (preferably 4 μm for small tubes and 10 μm for large tubes); and    -   applying a frequency of vibration of 20 to 100 kHz (preferably        20 kHz+/−100 Hz for small and large tubes).

The sonication time is around 3 minutes for small and large tubes. Themethod is able to crack all bacteria, viruses, spores, yeasts and moldwithout destroying their NA when performed in the appropriate buffermedium, i.e. guanidine buffer.

The above defined parameter ranges turned out to cover a wide variety ofsonication applications using the apparatus of the invention. Acontroller can be provided in the apparatus for allowing setting of therespective values within the ranges through a suitable operatorinterface and for controlling the components in the apparatus so thatthe sonication is effected within the set values. Further, thecontroller can also effect the automated transfer of the rack into andout from the apparatus as described above by activating the respectivedrive mechanisms in the apparatus in a predefined manner.

EXAMPLES Example 1 Demonstration of the Lysis Efficiency onMicroorganisms

1.1. Experimental Protocols

Preparation and Lysis of the Strains

For each tested microorganism, few CFUs (colony forming units) fromplate cultures are re-suspended in peptone salt diluent to a defined ODvalue. Ten-fold serial dilutions are realized.

Then, 10⁴ CFUs are spiked in lysis buffer (guanidine hydrochloride 1M,NLS 0.5%, 5 mM Tris pH 8, EDTA 0.5 mM). The total volume of the lysissolution is 500 μL. 10 replicate tests are realized.

The samples are sonicated with the apparatus according to the presentinvention in 1.5 mL sonication-resistant tubes (Eppendorf Safe-LockBiopur) for ca. 3 minutes. A DNA purification step is immediatelyperformed to isolate microorganism DNA in a real-time PCR compatibleelution buffer.

DNA Purification

Magnetic DNA purification is performed to purify microorganism DNA usingmagnetic beads. 15 samples are purified simultaneously employing theKingFisher instrument (ThermoScientific ref.5400050) and the MilliPrepkit (Merck Millipore ref. MPRPMYC48).

Afterwards, the eluates are transferred into 1.5 mL tubes andcentrifuged for 90 s at 10 000 g. If needed, the samples are stored at−20° C. and thawed before performing the specific real-time DNAamplification.

Specific Real-Time DNA Amplification and Detection

Except for L. monocytogenes and E. coli, specific real-time SYBR GreenPCR assays are performed. A 15 μL PCR mix per reaction is prepared with2× concentrated QuantiTect® SYBR® Green PCR kit (Qiagen) and 0.5 μM ofspecific primers. Then, 10 μL of each sample are added to each well.Negative controls (10 μL of water) and positive controls (1-100 ng ofthe tested microorganism gDNA) are incorporated in each run. Two PCRreplicate tests per purified sample are realized.

The PCR plates (Twintec plate, Eppendorf) are sealed (Microseal® film,Bio-rad) and centrifuged for 2 minutes at 1700 rpm. The PCR assays areperformed on the Mastercycler epgradient realplex² (Eppendorf)instrument.

For E. coli, a specific real-time TaqMan PCR assay is performed. A 15 μLPCR mix per reaction is prepared with 2× concentrated QuantiFast™ PCRkit (Qiagen), 0.1 μM of specific primer and 0.08 μM of a specific probe.Then, 10 μL of each sample are added into each well, with negative andpositive controls. Two PCR replicates per purified sample are realized.The PCR plates and assays are performed as described above.

The L. monocytogenes test is performed, using the FoodProof® ListeriaMonocytogenes Detection Kit (Biotecon Diagnostics). Two PCR replicatesper purified sample are realized. The PCR plate (FrameStar®, 4titude) issealed (QPCR Adhesive Clears, 4titude) and centrifuged for 2 minutes at1700 rpm. The PCR assay is performed on the Stratagene Mx3005P (AgilentTechnologies) instrument.

1.2. Results

Number of lysed Strain Av. Ct value ± stdev CFUs E. faecalis 21.72 ±0.508 8379 S. aureus 24.87 ± 0.384 9675 S. agalactiae 26.78 ± 0.340 16380 S. epidermidis 25.33 ± 0.205 10 870 L. monocytogenes 29.13 ± 0.4587664 P. aeruginosa 21.03 ± 0.192 16 550 S. enterica 23.23 ± 0.317 9113E. coli 24.23 ± 0.194 7790 P. acnes 23.97 ± 0.204 5280 C. sporogenes27.23 ± 0.599 5880 Spores of 27.82 ± 0.479 10 110 G. stearothermophilusZ. bailii 22.39 ± 0.77  12 830 C. albicans 21.66 ± 0.456 7976 C.neoformans 25.46 ± 0.503 9328 S. cerevisiae 28.78 ± 0.824 9250 Spores ofA. brasiliensis 21.56 ± 0.563 5100

The data show that sonication can be considered as an efficient lysismethod on Gram negative bacteria, Gram positive bacteria (includinganaerobic bacteria), spores of bacteria, yeasts and spores of molds.

Example 2 Demonstration of the Lysis Linearity

2.1. Experimental Protocols

The linearity of the lysis using the sonication apparatus according tothe present invention is tested by spiking and lysing 10/100/1000/10 000CFUs of the tested microorganisms (prepared as described above). 5replicates per tested concentration are realized. Purification and DNAamplification are realized as described above.

2.2. Results

Strain Av. Ct value ± stdev Lysed CFUs R² S. enterica 33.49 ± 0.98  80.9648 30.97 ± 0.53  116 27.32 ± 0.33  1160 23.68 ± 0.26  11 600 S.aureus 33.22 ± 1.065 13 0.9175  31.5 ± 1.064 157 28.40 ± 0.556 157024.91 ± 0.413 15 700 C. albicans 29.55 ± 1.226 9 0.9547 26.63 ± 0.868 8623.85 ± 0.405 860 20.68 ± 0.425 8602 A. brasiliensis 36.99 ± 1.022 160.9866 32.23 ± 0.597 92 26.29 ± 0.440 920 20.69 ± 0.772 9200 P.aeruginosa 31.36 ± 0.937 12 0.9836 27.51 ± 0.264 102 24.24 ± 0.150 101720.68 ± 0.215 10 166

The data presented in the table above show that the lysis of the testedmicroorganisms is linear using the sonication instrument.

1. An apparatus for performing sonication on liquid samples, comprising:a rack (1) for holding an array of sample vials (2); an ultrasonic probe(3) with an arrangement of recesses (4) corresponding to the array ofsample vials (2) and adapted to respectively receive and contact anouter surface of a bottom portion (2 a) of a respective one of thesample vials (2); and a counter-holder (5) with an arrangement ofpushing members (6) corresponding to the array of sample vials (2) andadapted to respectively apply a force to a respective one of the samplevials (2) so as to push the bottom portion (2 a) of each vial (2) intocontact with the associated recess (4) of the probe (3).
 2. Theapparatus of claim 1, wherein the pushing members are in the form ofpushrods (6) and are arranged to apply the force to a top portion of therespective associated vials (2).
 3. The apparatus of claim 2, whereinthe pushrods(6) are supported such that the force is adjustable and/orthe pushrods are elastically biased towards the vials (2).
 4. Theapparatus of claim 1, wherein a positioning mechanism (7) is provided toselectively engage the pushing members (6) with the vials (2).
 5. Theapparatus of claim 4, wherein the positioning mechanism (7) comprises aplatform (8) for holding the array of pushing members (6), said platform(8) being supported so as to be at least movable in the directiontowards and away from the probe (3) and including a drive mechanism foralternatingly moving the platform (8) in this direction.
 6. Theapparatus of claim 1, wherein the rack (1) is movably supported in thedirection of the center axes and elastically biased in a directiontowards the pushing members (6).
 7. The apparatus of claim 1, furthercomprising a moving mechanism for moving the rack (1) between a positionoutside of a housing of the apparatus and a position inside the housingaligned with the ultrasonic probe (3).
 8. The apparatus of claim 1,wherein the recesses (4) are formed to match a bottom configuration ofthe vials (2) in the array, wherein the recesses (4) are preferablyrotational symmetrical about a center axis, more preferablyhemispherical or conical.
 9. The apparatus of claim 8, wherein eachrecess (4) is configured so as to match different bottom configurationsof at least two different vials (2) and preferably has a rounded bottomportion (4 a) and a conical peripheral portion (4 b).
 10. The apparatusof claim 8, wherein at least the portion of the probe (3) containing therecesses (4) is exchangeable to accommodate a different array of samplevials (2) and/or sample vials (2) with different bottom configuration.11. A method of preparing a sample for detection of cell components,comprising: providing the sample in a sample vial (2), placing thesample vial (2) in the apparatus as defined in claim 1, performingsonication on the sample in the sample vial (2) by the apparatus usingthe following parameters to effect a lysis of the sample: applying amechanical stress in between the sample vial and the probe of 0.1 to1N/mm², applying a peak-to-peak amplitude of vibration of 2 to 10 μm,and applying a frequency of vibration of 20 to 100 kHz.
 12. The methodof claim 11, wherein plural samples are provided in plural sample vialsin the array and the sonication is simultaneously performed in theapparatus on the plural samples in the array.
 13. The method of claim11, wherein the sample(s) is/are provided in a sample volume of 20 μl to1 ml in sample vial(s) having a rated volume of 200 μl to 50 ml.
 14. Themethod of claim 11, wherein the sample vial(s) used for receiving thesample(s)is/are standard laboratory tubes, preferably conical laboratorytubes, so called 50 ml conical centrifuge tubes or round-bottom tubes,so called 1.5 ml or 2 ml microcentifuge tubes, or multi-well ormicrotiter plates, preferably made from plastics material including PP,PS, PC and PET.